I. Field of the Invention
The present invention relates generally to antennas for wireless devices. More specifically, the present invention relates to a dielectric and patch resonator antenna assembly that uses a patch element disposed between a ground plane and a dielectric resonator to provide GPS signal reception.
II. Description of the Related Art
Recent advances in wireless communication devices, such as mobile and fixed phones for use in satellite or cellular communications systems, have motivated efforts to design antennas more suitable for use with such devices. New antennas are generally needed to meet design constraints being imposed on new devices including overall size, profile, weight, and manufacturability. Several factors are usually considered in selecting an antenna design for a wireless device or phone, such as the size, the bandwidth, and the radiation pattern of the antenna.
The radiation pattern of an antenna is a very significant factor to be considered in selecting, an antenna. In a typical application, a user of a wireless device such as a mobile phone needs to be able to communicate with a satellite or a ground station that can be located in a variety of directions relative to the user. Consequently, an antenna connected to the wireless device should preferably be able to transfer, transmit and/or receive, signals from may directions. That is, the antenna should preferably exhibit an omni-directional radiation pattern in azimuth and a wide beamwidth (preferably hemispherical) in elevation.
Another factor that must be considered in selecting an antenna for a wireless device is the antenna bandwidth. That is, the useful range of frequencies over which the antenna efficiently transfers signals without an undesirable amount of loss. As an example, a typical wireless phone transmits and receives signals at separate frequencies. For example, a Personal Communication Services or PCS type phone operates over a frequency band of 1.85-1.99 GHz. requiring a bandwidth of 7.29%. A typical cellular phone operates over a frequency band of 824-894 MHz which requires an 8.14% bandwidth. Some satellite communication systems may have even wider bandwidth requirements. Accordingly, antennas for wireless phones used in such systems must be designed to meet these larger bandwidths.
Currently, monopole antennas, patch antennas, and helical antennas are among the various types of antennas being used in satellite user terminals or phones and other wireless-type devices. These antennas, however, have several disadvantages, such as limited bandwidth and large size. These antennas also exhibit a significant reduction in gain at lower elevation angles (for example, around 10 degrees), which makes them undesirable for use in satellite phones where a given satellite used for communication may frequently be near this low elevation.
An antenna that appears attractive for use in wireless user terminals or phones is the dielectric resonator antenna. Generally, dielectric resonators are fabricated from low loss materials that have high permittivity. Until recently, dielectric resonator elements have only found use in microwave circuits, such as in filters and oscillators. However, dielectric resonator antennas have been proposed and designed for wireless applications as described in U.S. patent application Ser. No. 09/150,157 entitled "Circularly Polarized Dielectric Resonator Antenna" filed Sep. 9, 1998, assigned to the same assignee, and incorporated herein by reference.
Dielectric resonator antennas offer several advantages over other antennas, such as small size high radiation efficiency, and simplified coupling schemes for various transmission lines. The bandwidth can be controlled over a wide range by the choice of dielectric constant (.di-elect cons..sub.r), and the geometric parameters of the resonator. Such antennas can also be made in low profile configurations, making them more aesthetically pleasing than standard whip, helical, or other upright antennas. A low profile antenna is also less subject to damage than other upright style antennas. Therefore, dielectric resonator antennas appear to have significant potential for use, for example, in mobile or fixed wireless phones for satellite or cellular communications systems.
Another issue facing many wireless device designers is the use of or proposal to incorporate GPS capabilities in such devices as an added feature. GPS allows the provision of location information to a device user or for triggering other information relative to a users location. It also allows accurate location of the user by the communication system in an emergency or for providing other services. GPS location accuracy is in fact being required for future wireless devices by various governmental bodies.
The GPS operates in the L-band and requires the use of an antenna for those frequencies, especially where most wireless devices communicate in other frequency bands, such as listed above. Therefore, implementing GPS related signal processing and services necessitates an additional antenna and consumes extra room to position the additional GPS antenna within the device. While GPS can utilize a relatively small patch antenna element, it is still an inconvenience to manufacture a device with a completely separate antenna element. It is also very difficult and sometimes commercially impractical to allocate such extra space and position the patch in a manner that operation is not inhibited by other components within the wireless device, without making the device unacceptably bulky, or non-asthetic, not to mention dramatically more expensive. Space and component positioning is at a premium in most modern wireless devices and antenna assemblies. Size is considered a very large henderance to marketability. In some applications such as in the case of mobile satellite phones, any increase in size also negatively impacts aerodynamics of external antennas.
In any case, it is very inconvenient and sometimes impractical to manufacture antenna assemblies with multiple antennas having two or more signal leads per antenna element, along with associated cables, connectors, and matching circuits. Each item or component, including cables, added to multiple antenna structures consumes room, making the structure undesirably larger, and makes it more difficult to physically assemble. It is also evident that the more components involved in any assembly make it more costly to manufacture, and may decrease operational reproducibility and reliability.
What is needed is an antenna structure that can maintain a desired polarization configuration, provide efficiently tailored radiation patterns, while allowing a simplified signal transfer process for GPS signals that are also to be used by a wireless device.